I have been 745i enthusiastic for about 20 years now and most of the time I've run the cars at higher boost levels (approx. 400 HP/670 Nm) with modified tuning chips. I have gathered quite a lot info on the BMW turbo and have also chips available for all versions of Motronic 0 261 200 013 and 0 261 200 024 boxes. Please check my web pages at
http://www.elisanet.fi/kingshill/745i/index.htm